Preparation of 1-hydroxy-2-alkane-sulfonates



United States Patent 3,230,250 PREPARATION OF I-HYDROXY-Z-ALKAWE- SULFONATES Alexander J. Stirton, Philadelphia, Frank D. Smith, Huntingdon Valley, and James K. Weii, North Wales, Pa, assignors to the United States of America as represented by the Secretary of Agriculture No Drawing. Filed Jan. 16, 1963, Ser. No. 251,985 4 Claims. (Cl. 260-513) (Granted under Title 35, US. Code (1952), see. 266) A non-exclusive, irrevocable, royalty-free license in the invention herein described, throughout the world for all purposes of the United States Government, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

This invention relates to 1-hydroxy-2-alkanesulfonates, derivatives thereof, and method of preparation. The compounds of this invention are useful as chemical intermediates, surface active agents, detergents, and lime soap dispersing agents.

An object of the present invention is to provide a process for the preparation of 1-hydroxy-Z-alkanesulfonates of the general formula RCH(SO M)CH OH, wherein R is a normal alkyl group having 7 to 16 carbon atoms and M is sodium, potassium, lithium, or hydrogen.

Another object of this invention is to prepare compounds of the general formula RCH(SO M')CH OSO M', wherein R is a normal alkyl group having 7 to 16 carbon atoms and M is sodium, potassium, or lithium.

A further object is to prepare compounds for use as the active ingredient in products such as solid detergent compositions, liquid syndet compositions, detergent bars, or in soap-detergent combinations.

Other objects and a fuller understanding of the present invention may be had by referring to the following description and claims.

In general according to the present invention an ester of the general Formula I RCH(SO M) CO R (I) wherein R is a normal alkyl group containing 7 to 16 carbon atoms, R is methyl, ethyl, n-propyl or isopropyl and M is sodium, potassium or lithium, a substantially anhydrous solvent and dispersing medium consisting of a low molecular weight primary or secondary alcohol, and a metal borohydride such as sodium borohydride or lithium borohydride, are combined, and the mixture is heated until the reaction is substantially complete, to form a lhydroxy-Z-alkanesulfonate of the general formula II RCH ($0 M) CH OH (11) wherein R and M remain unchanged.

3,230,250 Patented Jan. 18, 1966 The discovery that an alkali metal salt of an alkyl ester of a long chain a-sulfo fatty acid could be smoothly and selectively reduced at the carboxylic ester group to give the corresponding primary alcohol group was unexpected. The inertness of the sulfo group under the conditions of the reaction was not predictable. Even more surprising, and contrary to previously reported information, is the discovery that sodium borohydride is an elfective reducing agent for the carboxyl function in the ester group.

The esters of general Formula I are prepared by well known procedures, sulfonating a fatty acid with S0 or ClSO H, as illustrated by the equation,

esterifying the a-SlllfO fatty acid product at the carboxyl group:

and then neutralizing as follows:

RCH (SOgH) CO R'-+MOH a RCH M CO R'+H O (3) to give the same product, as illustrated by Equations 4 and 5:

The reaction to produce the l-hydroxy-Z-alkanesulfomates of the present invention is considered to proceed according to the following equation:

While the reaction gives high yields of the indicated product, a side reaction proceeds as follows:

Since this product, the salt of the a-sulfo fatty acid, may be recovered and used again in the esterification and reduction reactions, the yield of l-hydroxy-Z-alkanesulfonate from starting material is substantially 100%.

In a preferred embodiment of the present invention a compound of the general Formula I, where M is sodium or lithium, and R is methyl or isopropyl, is combined in isopropanol with about a 1.2 to 2.4 molar ratio of sodium borohydride or lithium borohydride, the mixture is heated at reflux temperature for several hours, and a l-hydroxy- 2-alkanesulfonate separated from the reaction mixture.

The 1-hydroxy-2-alkanesulfonate is a useful chemical intermediate, detergent and surface active agent. It may be sulfated at the primary alcohol group:

or the primary alcohol group may be employed in esterification reactions with organic carboxylic acids or sulfocarboxylic acids.

In another embodiment of the invention the reduction product is separated as the free sulfonic acid by the use of ion exchange techniques, as illustrated in the equation:

RCH M) CH OH+H+ RCH(SO H)CH OH+M+ (9) then sulfated and isolated as the salt,

RCH(SO M)CH OSO M usually as the less expensive disodium salt. Sulfation is preferably carried out on isolated l-hydroxy-Z-alkanesulfonic acid in chloroform by means of a 1.4 to 1.7 molar ratio of chlorosulfonic acid.

While the invention is exemplified with esters derived from commercially available fatty acids such as pelargonic, lauric, myristic, palmitic and stearic acids, the process is considered applicable to esters derived from fatty acids having 9 to 18 carbon atoms, or mixtures thereof.

Preferred esters are those in which the alcohol moiety is obtained from methanol or isopropanol, but R may be derived from other short carbon chain primary or secondary alcohols such as ethanol, n-propanol, n-butanol, or isobutanol.

Although other types of metal borohydride reductions, such as reduction of ketones with sodium borohydride, are reported to proceed satisfactorily in aqueous systems, the process of the present invention is, at least for all practical purposes, operative only in anhydrous systems.

The solvent is preferably a low molecular weight primary or secondary alcohol. Isopropanol is the especially preferred solvent because its solubility and boiling point characteristics are conducive to higher yields of the desired product than those obtainable with other low mo lecular weight alcohols.

Yield of the 1-hyd roxy-2-alkanesulfonate is also im proved by using an excess of the reducing agent, preferably a ratio of 1.2 to 2.4 moles of sodium borohydride or lithium borohydride per mole of ester.

The reaction mixture is heated, conveniently to the reflux temperature of the solvent, until the reaction is considered substantially complete. Various factors, such as solubility of substrate and reducing agent in the solvent, boiling point of the solvent, and choice of reducing agent, affect the time required to obtain optimum yield of 1- hydroxy-Z-alkanesulfonate. While many reductions are complete in a few hours, some were allowed to continue 24 hours to provide ample time for complete reaction.

Since the 1-hydroxy-2-alkanesulfonates of general Formula II are not very soluble in water, especially when M is sodium, a convenient means of separating the product from the reaction mixture is to evaporate most of the solvent and add water, thus converting the borohydride reducing agent to water soluble products and precipitating the 1-hydroxy-2-alkanesulfonate so that it may be recovered as a solid.

The product may be further purified, as by recrystallization from methanol.

In operating the process to obtain definite chemical compounds for purposes of comparative evaluation the same metal (M) Was selected for the ester and for the reducing agent. In many instances the production of 1- hydroxy-Z-alkanesulfonates which are a mixture of salts of potassium, sodium and lithium may be more practical or desirable. Regardless of the particular ester or reducing agent in the reaction mixture, the inclusion of the ion exchange step, producing the free sulfonic acid derivative, makes it possible to prepare the desired l-hydroxy-2-alkanesulfonates or mixture of alkanesulfonates, by neutralizing with a particular base or a mixture of basic materials.

Many ion exchange resins which are suitable for use in the process are available from commercial sources.

Yields of recrystallized 1-hyd-roxy-2-alkanesulfonate are usually about 60% or higher and the byproduct salt of the hydrolyzed ester is recovered for recycling.

Sulfation of the 1-hydroxy-2-alkanesulfonate to the 2- sulfoalkyl sulfate likewise proceeds in good yield, which could not have been predicted in view of possible dehydration and polymerization reactions.

Properties of the products of our invention are shown in Tables I, II, III, IV.

The Krafft point, a convenient indication of relative solubility, may be defined as the temperature at which a 1% turbid aqueous dispersion changes sharply to a clear solution on gradual heating. The critical micelle concentration, abbreviated as CMC, is the concentration at which simple ions or molecules aggregate to form col loidal micelles.

The alkali metal salts of l-hydroxy-Z-alkanesulfonic acids particularly those of 14 or more carbon atoms, have limited solubility, attributable to hydrogen-bonding. The corresponding free acids formed by ion exchange are, in contrast, easily soluble, as can be seen in Table H. Isolation of the free acid permits the easy formation of more readily soluble salts with aqueous ammonia, lower molecular weight amines and alkanolamines.

As can be seen from Table I the lithium salt is more soluble than the corresponding sodium 1-hydroxy-2-al kanesulfonate and the reduction of the lithium salt of an alkyl ester of an a-sulfo fatty acid can be carried out with LiBH and the product can be isolated as the soluble lithium salt RCH(SO Li)CH OH without the necessity of ion exchange.

Tables I, III and IV demonstrate that sulfation of the 1-hydroxy-2-alkanesulfonates of our invention improves solubility, detergent and foaming properties, particularly in the 18 carbon compound, increases the critical micelle concentration, and greatly improves resistance to precipitation by hard water and various metal ions. The 2-sulfoalkyl sulfates are easily soluble detergents and surface active agents, stable to alkaline hydrolysis and about as stable to acid hydrolysis as the related sodium alkyl sulfates. In particular the 18 carbon compound, disodiurn 2-sulfooctadecyl sulfate, is an excellent lime soap dispersing agent and therefore can be used effectively with soap in hard water to make useful soap-detergent combinations.

5 6 TABLE I I -hydroxy-Z-alkanesulfonates and Z-sulfoalkyl sulfates CH OH CMC b Elemental analysis, found/thee.

RCH Krafit point, C.

\ Percent Mmoles per Percent Na Percent Percent H Percent S $03M liter CHaOH 0 111 011 3 Ngglicelles, 1P, 9. 29/9. 34

SOaNa CHaOH CmHnCH 56 .43. 15. 0 8. 01/7. 97 50. 09/49. 98 8. 77/8. 74 11.13/11. 12

SOsNa CHzO H CuHflC 71 .11 3. 4 7. /7. 27 53. 13/53. 14 9. 09/9. 24 10. 21/10v 13 S O Na CHaOH CHHZBCfi 84 .010 3 6- 72/5. 68 56. 13/55. 78 9. 65/9. 66 9. 27/9, 31

S O Na C HzOH C HMC H 93 .0037 1 6- 12/6. 17 58. 08/58. 03 10. 02/10. 01 8. 99/8. 61

SO1N8 01120 H C HuC 73.5- 9. 83/10. 06

CHzOH CuHnCH 33-.-. d 2. (lo/1.96

SOBLi CHzO SO 3M C H2 0 S O 3N8 SO :N&

C H2O S 0 :N8

0 E 0 sogg lfility 15% at .17 3.6 9.65/9. 69 45. 51/45. 55 7. 61/7. 65 13. 60/13. 51

SO3Na Temperature at which a. 1% turbid dispersion becomes clear on gradual heating. b Critical micelle concentration.

Percent K. 5 Percent Li.

TABLE 11 1-hydroxy-2-alkanesulf0nic acids CHaOH Critical mlcelle concentra- Neutrallzatlon Melting tlon RCH equivalent, point, C. Krafit point, C.

\ found/thee.

S 0 11 Percent Milllmoles/l.

/CH2OH CmHnCH 265. 91266.4 108 Easily soluble .35 16. 1

below 25. SOzH /CH:OH CHHfiCH 294. 0/294. 4 111.5 d0 057 2. 61

S 0 3E /CH2OH (MH CH 322. 9/322. 5 114. 6 -do 021 O. 58

S 0311 /CH;OH CmHaOH 350. 0/350. 6 28.5 0078 0. 21

SOgH

TABLE III Detergency and foam Detergency, Terg-O-Tometer,

standard soiled cotton, Foam height Ross- CHiOH swatches/liter, 60 0., AR=in- Miles test, 60 C., mm.

crease in reflectance after washing ROH I SOsNa 0.25%, 0.25%, 0.25% 25% 25%,

distd. 300 p.p.m. built, distd. 300 p.p.m. water 300 p.p.m.

OHzOE SOsNa.

CHzOH CmHg CH 25. 0

sosNa CHaOH Cm aaC 26. 2

SOsNa CHzOH CmHnCH 24. 3

SOaNa CHzOSOaNa SOaNa CHIOSOQNS 014E290 1a. 2 16. 0 15. 9 s 190 SOaNa CH2OSOaN8 CroHaaCH 26. 8 22. 3 22. 1 200 205 SO3Na I Concentration of .05% active ingredient, 0.2% inorganic polyphosphate-phosphatew sulfate builder.

TABLE IV Surface active properties of disodium Z-sulfoalkyl sulfates Surface Wetting time, seconds,

Solubility tension, Draves test b Oa++ Lime soap C. 0M0,- dynes stability,= Metal ion Stability to dispersing percent percent per cm., p.p.m. stability Hydrolysis e power,

25 0., .1% distd. .1% 300 08.00; percent .2% water p.p.m.

CHzOSOaNa 7 i Values oi'lUO CuH CH 7 .4 55.4 180 84 1,800 fE fi L- lq fi g l 85 1 E inc y ro SOaNa gaz, ysis.d Elylglrfi n yze 1n CHaOSOaNB i rff ai -l1 H01 g CmHgaCH 15 .11 4o. 2 2s 42 1,sou g ig at 100 5 SOaNa gritical micelle concentration.

.A.T.C.O. Tech. Manual 36, 161-3 (1960), standard test methd s Wilkes and Wickert, Ind. Eng. Chem. 29,12349 high as 1,800 means complete stability to hard water.

(1937). A value as d Detergency Evaluation and Testing, by I. C. Harris, pages 224 ion.

. A value as high as 100 means complete stability to this metal The following examples further demonstrate the products and the process of our invention.

EXAMPLE I LiBH reduction of Li isopropyl u-sulfostearate.-

in 270 ml. of isopropanol was heated and ml. of the solvent was distilled to remove traces of moisture. ness. The residue was" taken up with 1200 ml. of wa- The disodium Z-sulioalkyl sulfates like the sodium alkyl sulfates are not hydrolyzed in alkali but can be hydrolyzed in hot acid solutions.

1 Borghetty and Bergman, J. Am. Oil Chemists Soc. 27, 88-90 (1950). A value of 5% is excellent and means that 5 grams will disperse the Ca soap formed from grams of Na oleate.

Lithium borohydride (1.48 grams, 68.5 millimoles) was added during 3 minutes, the solution was refluxed 24 hours, 300 ml. of water was added and the mixture was sulfonic acid (Dowex SOW-X8), the eluate neutralized with sodium hydroxide to pH 10.0 and evaporated to dryter, heated to boiling, allowed to crystallize at room temperature, filtered, washed, dried at 60 in a vacuum oven and extracted twice with 3 l. of boiling methanol. The residue insoluble in methanol was the hydrolyzed unreduced ester recovered as disodium a-sulfostearate, yield 39%. Crystallization of the methanol extract gave C I-I CH(SO Na)CI-I OH, yield 61% with the analysis and properties shown in Tables I and III.

EXAMPLEv II NaBH reduction of Na methyl ot-sulfstearate.A solution of 8.0 grams (20.0 millimoles) of in 150 ml. of isopropanol was heated and 25 ml. of solvent was distilled to remove traces of water. Sodium borohydride (1.76 grams, 46.5 millirnoles) was added during 3 minutes and the mixture was refluxed for 24 hours. Separation of the 1-hydroxy-2-alkanesulfonate from hydrolyzed ester gave 44% yield of C15H33CH and 56% recovery of disodium a-sulfostearate.

EXAMPLE III LiBH, reduction of Li methyl ot-sulf0myristate.A solution of 41.4 grams (126 millimoles) of was dissolved in 450 ml. of isopropanol and 50 ml. was distilled to remove traces of moisture. Lithium borohydride (3.44 grams, 158 millimoles) was added during 3 minutes and the mixture was refluxed 24 hours. Separation as described in Example I gave 74% yield of C H CH(SO Na)CH OH and 26% recovery of disodium a-sulfomyristate.

EXAMPLE IV l-hydr0xy-2-alkanesulf0nic acids.-Sodium l-hydroxy- 2-hexadecanesulfonate, 2.9 grams, was dissolved in 1 50 ml. of isopropanol by heating and stirring in the presence of 100 ml. of resin sulfonic acid (Dowex 50W-X8), passed through a column containing 300 ml. of the exchange medium and eluted with 900 ml. of isopropanol.

The isopropanol solution was evaporated in a rotary evaporator at 80 C. and mm., the residue was dissolved in 100 ml. of chloroform and water was removed azeotropically. Crystallization from chloroform at 20 C. and drying for 1 hour in a vacuum oven gave l-hydroxy-2-hexadecanesulfonic acid with the analysis and properties shown in Table II. The 1-hydroxy-2-alkanesulfonic acids of our invention are hydroscopic crystals which soften and pass through a glassy stage before melting sharply at the temperatures listed in Table II.

EXAAIPLE V Sulfaiion 0 1-hydroxy-Z-alkanesulfonic acids. Disodium-Z-sulfooctadecyl sulfate.Chlorosulfonic acid (12.2 1111., 21.5 grams, 185 millirnoles) was added slowly in 1.7 molar ratio to a stirred slurry of 37.9 grams (108 millimoles) of C H CH(SO H)CH OH in 500 ml. of carbon tetrachloride at 23 C. A clear solution developed during the addition, HCl was evolved and the temperature dropped to C. The mixture was stirred and heated at 2045 C. for 20 minutes, with a slight color development.

The sulfation mixture was cooled to 0 C., 200 ml. of 95% ethanol was added, and the mixture was made slightly alkaline with aqueous 18 N sodium hydroxide. The precipitated solids were filtered off, treated with 60% ethanol, and filtered. Crystallization of the aqueous alcohol filtrate at 0 C. gave an 82% yield of disodium 2-sulfooctadecy1 sulfate, purity 92%, further purified by crystallization from 80% ethanol at 0 C. to give disodium 2-sulfooctadecyl sulfate in a pure state, yield 77%, with the analysis and properties shown in Tables I, III,

and IV. Disodium 2-sulfohexadecyl sulfate was obtained in a similar manner.

We claim:

1. A process for the preparation of 1-hydroxy2-alkanesulfonates comprising combining (a) an ester of the formula wherein R is a normal alkyl group containing 7 to 16 carbon atoms, R is selected from the group consisting of methyl, ethyl, n-propyl, isopropyl, n-butyl, and isobutyl, and M is selected from the group consisting of sodium, potassium, and lithium, and (b) sodium borohydride, in (c) a substantially anhydrous alcohol selected from the group consisting of low molecular weight primary and secondary alcohols to provide a reaction mixture, and heating said mixture until the reaction is substantially complete, said reaction comprising reducing the carboxyl moiety of the ester and forming a l-hydroxy-Z- alkanesulfonate of the formula RCH(SO M CHgOH wherein R and M have the same significance as above. 2. The process of claim 1 in which R is C H M is sodium, and the 1-hydroxy-Z-alkanesulfonate is c n cmso rmcn on 3. A process for the preparation of 1-hydroxy-2-alkanesultonic acids comprising combining (a) an ester of the formula wherein R is a normal alkyl group containing 7 to 16 carbon atoms, R is selected from the group consisting of methyl, ethyl, n-propyl, isopropyl, n-butyl, and isobutyl, and M is selected from the group consisting of sodium, potassium, and lithium, and (b) sodium borohydride, in (c) a substantially anhydrous alcohol selected from the group consisting of low molecular weight primary and secondary alcohols to provide a reaction mixture, heating said mixture until the reaction is substantially complete thereby producing a l-hydroxy-Z-alkanesulfonate of the formula RCH(SO M) CH OH wherein R and M have the same significance as above, mixing the reaction mixture with water, contacting the 1-hydroxy-2-alkanesulfonate contained in the resulting aqueous alcohol solution with an excess of ion exchange resin in the acid cycle, and separating from the aqueous alcohol solution a 1-hydroxy-2-alkanesulfonic acid of the formula RCH(SO H)CH OH wherein R has the same significance as above.

4. The process of claim 3 in which the ester is C H CH(SO Na)CO CH and the l-hydroxy-Z-alkanesulfonic acid is C H CH(SO H)CH OH.

References Cited by the Examiner UNITED STATES PATENTS 2,264,759 12/1941 Jones 260458 2,267,731 12/1941 Guenther et a1 2605 13 2,335,193 11/1943 Nawiasky et al 260513 2,402,823 6/1946 Kyrides 260513 X 2,709,686 5/1955 Lewis et al. 25216l 2,743,288 4/1956 Rueggeberg et al. 260400 2,810,746 10/1957 Rueggeberg et a1. 260513 2,822,387 2/1958 Bloch 260--513 2,909,554 10/1959 Doerr 260458 3,147,301 9/1964 Sheetz 260513 X FOREIGN PATENTS 838,215 5/ 1952 Germany.

(Other references on following page) 1 1 1 2 OTHER REFERENCES Schenck et al.: J. Am. Chem. Soc., vol. 75, pp. 1636- z 0 Ch 19 1 1641 (1953). 52253 Fleser Advanced rgamc W W11lems: Bull soc. chim Belg., vol. 64, "pp. 409-441 Gaylord: Ibid., p. 8 51. Gaylord: Reduction with Complex Metal Hydrides, 5 Wlllems' 11952 3 (1956) PP- 500-509 (1956)- LORRAINE A. WEINBERGER P E Houben-Weyl: Methoden der Organischen Chemie, nmary xammer' CHARLES B. PARKER, Examzner.

vol. 9, pp. 349-359 (1955).

Puschel et al.: Ber. Deut. Chem., vol. 97, No. 10, p. 10 F. HIGEL, B. M. EISEN, M. WEBSTER,

2916. Assistant Examiners. 

1. A PROCESS FOR THE PREPARATION OF 1-HYDROXY-2-ALKANESULFONATES COMPRISING COMBINING (A) AN ESTER OF THE FORMULA 